Study Of Alkaline Hydrolysis And Air Stripping United Treament Of Production Wastewater Of Imidacloprid

Large amounts of pesticides are produced and used each year and pesticide industry also plays an important role to the economy of China.Efficient insecticide imidacloprid called "neonicotinoid" compound has been the representatives of the new generation of pesticides due to its high efficiency,low toxicity and other advantages.However,the wastewater generated during its production process contains toxic and refractory organic matters,making it difficult to remediate.The main ingredients are imidazolidine and N,N-dimethylformamide(DMF),which leads to high concentration of organic nitrogen.Therefore,the efficient removal of imidazolidine and DMF becomes the key factor in treating imidacloprid wastewater.This study adopted alkaline hydrolysis to remove the imidazolidine and DMF.The operation conditions were optimized and the intermediate is determined.Afterwards,the stripping experiment is conducted to remove the nitrogen.During the alkaline hydrolysis experiment,the influence of temperature,pH and duration on the removal performance were investigated.The results showed that the pH of 13,the temperature of 50? and time of 2.5 hours is optimal for the removal of DMF.The concentration of DMF reduced from 3800 mg/L to 128.1 mg/L.On the other hand,the optimal conditions for the removal of imidazolidine is pH:12,temperature:60?,time:2.5 hours.The best removal rate of imidazolidine reached 97.6%.The LC-MS analysis results showed that the alkaline hydrolysis products of imidazolidine and DMF included imidazolidinone,dimethylamine and formates.Based on the above conclusions,we determined the best reaction conditions for the alkaline hydrolysis of imidacloprid wastewater.The removal efficiencies of imidazolidine and DMF were 97.0%and 95.1%,respectively.Followed by the alkaline hydrolysis,air stripping technique was investigated to study the effects of pH,temperature and gas-liquid ratio on the nitrogen removal performance.Results indicated that the optimum conditions for air stripping is pH:12.3,temperature:40?,the gas-liquid ratio:3000:1.The removal rate of KN reached 95.7%(from 839mg/L to 36 mg/L).Finally,the KN and COD concentration of the wastewater is only 36 mg/L and 2480 mg/L after alkaline hydrolysis and air stripping,which can be subjected to the following biological treatment.